1. Field of the Invention
This invention relates to packet video bitrate conversion systems and, more particularly, packet video bitrate conversion systems which are suitably used when video conferences are held in circumstances constituted by various networks and beyond these networks.
2. Description of the Related Art
Heretofore, video conferences are held by inter-connecting various networks using gateways or the like. In such a case, the bitrate of the video transmission is limited to the bitrate of the lowest bitrate network. This means that video bitrate converters are necessary to hold video conferences.
A prior art video bitrate converter decodes coded video data and then re-encodes the decoded video data at a desired bitrate. Another prior art video bitrate converter which is disclosed in Japanese Laid-Open Patent Publication No. 4-3684, encodes video data by layered coding into high priority data and low priority data to be transmitted, and deletes the low priority data when the network is congested.
The former prior art video bitrate converter, however, dictates complicated processes as decoding and re-encoding video data to be performed in a gateway, which connects a LAN and a line connecting remote LANs. Inevitably, the gateway has a complicated construction, increasing equipment cost and process delay.
The latter prior art video bitrate converter, has a problem that the bitrate cannot be freely converted in a gateway, because of the fact that the ratio between high and low priority data is fixed when encoding the video data.